Pinch valve

Abstract

This invention provides a pinch valve having a pinch region defined by a pair of rotating pinch elements. These pinch elements define a variable profile that substantially surrounds the entire circumference of a tube in the pinch region and that thereby ensures that the tube is always returned to the desired opening size at all valve adjustment settings in a range from fully open to fully closed. More particularly, the pinch elements are provided with a pinch region that defines a surface geometry that includes a continuously variable-length (ramping) linear segment, disposed at a continuously variable depth (ramping from full open to fully pinched), that pinches the walls into a pair of opposed parallel lines throughout the majority of their rotational movement/adjustment range. The pinch elements also include upper and lower variably sized fillets (typically curved) on each side of the linear segment that capture the curved top and bottom of the tube, adjoining the pinched walls, so as to force the top and bottom back into a desired shape despite the presence of any permanent deformation of the walls. Overall, the pinching region is adapted to conform to the prevailing outline of the tube at the pinch point throughout the range of pinch settings. In an illustrative embodiment, the pinch elements counter-rotate, so that parallelism between opposing pinched walls is enhanced.

1. A pinch valve comprising:
 a housing that encloses a flexible tube; 
 a first pinch element and a second pinch element, each being oriented on a respective axis of rotation transverse to an axis of extension of the tube, each of the first pinch element and the second pinch element being constructed and arranged to rotate with respect to each other between a fully closed and a fully open position; and 
 wherein each pinch element respectively defines a pinch region that confronts an outer wall of the tube to define a profile that surrounds substantially the outer perimeter of the tube, the pinch region varying about a circumference of each of the first pinch element and the second pinch element between (a) the fully open position in which the profile conforms to a shape of an outer perimeter of the tube in an unpinched state, through (b) a continuous ramping surface in which the profile at various points around the circumference defines, for pinching the tube, progressively from a shortened flattened segment at large depth with respect to the axis of extension and large-radius filleted ends to a lengthened flattened segment of small depth with respect to the axis of extension and small-radius filleted ends to (c) the fully closed, position in which the profile defines, a maximum length flattened segment at minimum depth with respect to the axis of extension and minimum-radius filleted ends, whereby the tube is substantially engaged along substantially the outer perimeter by the pinch region at all circumferential positions of the pinch elements. 
 
   
   
     2. The pinch valve as set forth in  claim 1  the first pinch element is constructed and arranged to counter-rotate with respect to the second pinch element. 
   
   
     3. The pinch valve as set forth in  claim 2  wherein the first pinch element includes a first and the second pinch element includes a second gear and wherein the first gear engages the second gear to cause the first pinch element to rotate in response to rotation of the second pinch element. 
   
   
     4. The pinch valve as set forth in  claim 2  wherein the tube is fixedly attached into the housing and the housing includes end connectors for interconnecting with a fluid system. 
   
   
     5. The pinch valve as set forth in  claim 4  wherein the housing includes a first flared end and a second flared end, the tube includes a first shaped end that conforms to the first flared end and a second shaped end that conforms to the second flared end, a first sealed end cap with a first end connector engaging the first flared end and a second sealed end cap with a second end connector engaging the second flared end. 
   
   
     6. The pinch valve as set forth in  claim 1  wherein the first pinch element and the second pinch element each include cylindrical top and bottom sections that respectively bound the pinch region. 
   
   
     7. The pinch valve as set forth in  claim 6  wherein the housing includes wells for receiving the cylindrical top and bottom sections to restrain the pinch elements against lateral movement during rotation. 
   
   
     8. A pinch valve comprising:
 a housing that encloses a flexible tube; 
 a first pinch element and a second pinch element, each being oriented on a respective axis of rotation transverse to an axis of extension of the tube, each of the first pinch element and the second pinch element being constructed and arranged to counter-rotate with respect to each other between a fully closed and a fully open position; and 
 wherein each of the first pinch element and the second pinch element define one half of a profile that ranges along a circumference of rotation from a fully open shape in which the tube is unpinched to a fully closed shape, in which the tube is fully pinched together and wherein the profile, at all times through rotation from the fully open shape to the fully closed shape engages substantially an entire outer perimeter of the tube to force the tube to remain in the desired shape. 
 
   
   
     9. The pinch valve as set forth in  claim 8  wherein the pinch region varies about the circumference of each of the first pinch element and the second pinch element between (a) the fully open position in which the profile conforms to a shape of an outer perimeter of the tube in an unpinched state, through (b) a continuous ramping surface in which the profile at various points around the circumference defines, for pinching the tube, progressively from a shortened flattened segment at large depth with respect to the axis of extension and large-radius filleted ends to a lengthened flattened segment of small depth with respect to the axis of extension and small-radius filleted ends to (c) the fully closed, position in which the profile defines, a maximum length flattened segment at minimum depth with respect to the axis of extension and minimum-radius filleted ends.